IMPACT OF CLIMATE CHANGE ON FUTURE AVAILABILITY OF WATER FOR IRRIGATION AND HYDROPOWER GENERATION IN OMO-GIBE BASIN, ETHIOPIA

Abstract

Impacts of climate change could change how much water is available in the future for various uses. This study objective was to project the impacts of climate change and identify adaptation measures in order to increase the amount of water that will be available for irrigation and hydropower generation in the future. Climate change was projected using multi-model Regional Climate Change Models (RCMs) Coordinated Regional Climate Downscaling Experiment (CORDEX)-Africa models under two climate change emission scenarios RCP 4.5 and RCP 8.5.Future water availability magnitude, allocation, and demand for irrigation and hydropower generation were projected using an integrated approach using Soil and Water Assessment Tool (SWAT) and Water Evaluation and Planning (WEAP) hydrological models. Climate change was projected in three (3) windows: short term (2017 - 2044), medium-term (2045 - 2072), and long-term (2073 - 2100) were compared to the reference period (1987 – 2019). Mann-Kendall (MK) trend testing was used to determine if a change is statistically significant and to detect trends in temperature, precipitation, and streamflow. Significantly positive (rising) changes in temperature were predicted by emission scenarios under RCP4.5 and RCP8.5, but significantly negative (declining) changes in precipitation and streamflow. The projected annual average temperature increases were 2.41°C and 4.5°C under the RCP4.5 and RCP8.5 emission scenarios, respectively. The projected average annual decrease in precipitation and streamflow ranged from 10.7 % to 13.6 % and 11.1 % to 13.8 % and; 7.0 % to 10.9 % and 10.9 % to 12.8 % under the RCP4.5 and RCP8.5 emission scenarios respectively. The impact of climate change could lead to an 8.0 % to 25.1 % increase in future water shortages. As a result, water shortages for irrigation could increase by 15.5 - 25.4 % and hydropower generation by 10.5 - 20.2 % during the study periods 2017-2100. Under the combined effect of climate change and rising water demand, the increase in variation in water shortage ranges from 7.9 % to 30.6 %. Quantified and projected climate change impacts statistics showed that the future availability of water for irrigation and hydroelectric power generation will decrease in the future. In this study, two climate change adaptation options were identified to be effective in managing future water supply and demand sides and ensuring future water availability for irrigation and hydropower generation. The results of the study indicated that more research is needed to determine whether these options for coping with climate change are appropriate for potential climatic scenarios in the Omo-Gibe River basin.